Generator inertia for isolated hydropower systems

Speed regulation of hydroelectric power plants of isolated systems is a complex subject, which is now becoming more important as customers install computers, stereophonic equipment, and advanced satellite dish electronic equipment in such systems. This paper presents a methodology for determining hydroelectric generator inertia, based on theoretical analysis, coupled with a review of data from over 50 hydroelectric projects with units having capacities between 2 and 300 MW. The parameters that affect generator inertia—system size, allowable frequency variation, type of load, turbine and governor, water column start time, governor time, and relief valve operation— are all discussed. A chart combining these parameters is developed, on which data from hydro projects is plotted. From an analysis of the plotted data, an empirical equation is developed for the generator inertia as a function of the aforementioned parameters.